CZ287721B6 - Powder materials for formation of coatings - Google Patents

Abstract

In the present invention there are disclosed powder materials for formation of coatings that contain at least one polymeric material for formation of a film and two or a plurality of dry-mixed additives being selected from a group comprising solid, particulate, inorganic, water-insoluble materials, and namely ceramic or inorganic materials and/or oxides, mixed oxides, hydrated oxides, hydroxides, oxide-hydroxides or oxygenic salts and metalloids, whereby in at least 95 percent by volume of the material the particle size is at the most 50 micrometers.

Description

Technical field

The invention relates to powdered materials used to form films on the surface of substrates.

BACKGROUND OF THE INVENTION

Powder coating materials are a rapidly evolving field. These materials are solid compositions which are usually applied by electrostatic spraying, in which the powdered material particles in the spray gun are charged with an electrostatic charge, wherein the substrate is grounded or has an opposite charge. The powder coating particles are charged in the spray gun by applying stress or applying triboelectric friction. The deposited material is then heated up to the melting point and after setting the particles, the coating cures. Material particles that have not adhered to the substrate can be collected for reuse so that powder coating materials are very economical in use. In addition, these materials are solvent-free and in particular do not use organic solvents, so that environmental pollution cannot occur.

Coating materials usually comprise a solid resin capable of forming a film, usually together with one or more colored materials such as pigments, or may contain other additives to facilitate the coating. These are usually heat-curable materials, which include, for example, a film-forming polymer and a hardener, which may be another film-forming polymer. These materials are usually prepared by thoroughly mixing the ingredients, including color and coating facilitating components, for example in an extruder at a temperature above the softening temperature of the polymer or film-forming polymers, but below the temperature at which it could occur to a greater extent to a preliminary reaction. The extruded material is typically rolled into a flat film and then cut, for example, by grinding to the desired particle size. The particle size distribution required for most conventional electrostatic spray coating devices is in the range of 10 to 120 microns, with a mean particle diameter in the range of 15 to 75, preferably 25 to 50 microns, see, for example, WO 91/18951. These powder materials are typically applied with a film thickness of 40 to 50 microns and above.

When using powder materials with this conventional particle size distribution, it is difficult to apply thin film coatings having a thickness of, for example, 30 microns or less, but there is an increasing demand for such materials for certain purposes, especially where it is desirable to achieve uniform opacity and pleasant aesthetic appearance. especially in the case of glossy white coatings. In the meantime, such results can only be achieved with a limited choice of materials from a chemical point of view, generally the best results can be achieved using polyurethane-based powder materials using isocyanates. It is very difficult and perhaps impossible to achieve coatings with a thickness of less than 20 microns with uniform opacity and a pleasant aesthetic appearance. The problems associated with this, for example, the imperfect surface of the so-called "orange peel appearance" is probably due to the relatively large diameter of most particles in the material having a conventional particle size distribution.

In addition to the increasing demand for thinner coatings, it is clear that the impossibility of using powder coatings thinner than 30 microns with a pleasant aesthetic appearance is one of the factors preventing the substitution of solvent-based paints for the time being on a larger scale.

It is likely that the problems of achieving satisfactory thin coatings using powder coating materials could be alleviated if

Use powder materials with a smaller particle diameter. However, there are problems associated with fluidization, processing and deposition of relatively small particles, particularly particles having a diameter of 10 microns or less. These problems are exacerbated by the higher the proportion of fine particles, so that powder coating materials have hitherto been produced not to contain more than 10% by volume of particles with a diameter of 10 microns or less, see for example WO 91/18951.

SUMMARY OF THE INVENTION It is an object of the present invention to alleviate the problems associated with fluidization, processing and deposition of fine particles, in particular particles having a diameter of 10 microns or less, so as to substantially increase the proportion of such material particles while facilitating the formation of thin coatings with good appearance. Fluidization and processing behavior, especially spraying, can be determined for the powdered coating material by the so-called fluidity index (or "spraying factor") using an AS 100 flow meter (Sames, Grenoble).

In addition to fluidity, deposition, and coating problems, the invention also addresses the problems associated with preventing or alleviating various other problems associated with undesired uneven or premature electrostatic charge formation on powder material particles due to spontaneous triboelectric charge during mixing and deposition. powder materials. An important problem that arises from non-uniform electrostatic charges is the undesirable unevenness in the deposition of material at different voltages, leading to uneven coating of substrates. So-called electrostatic segregation, i.e. undesirable separation or uneven deposition of the two components of the powdered material on different parts of the substrate occurs during spraying.

SUMMARY OF THE INVENTION

The present invention provides powder coating compositions comprising at least one polymeric film-forming material and at least two dry-blended ingredients selected from solid, particulate, inorganic, water-insoluble, ceramic or mineral materials. and / or oxides, mixed oxides, hydrated oxides, hydroxides, oxide hydroxides or oxygenated metal salts and metalloids, wherein at least 95% by volume of the powder coating material has a particle diameter of less than 50 microns.

By using the dry blend combinations of the present invention, problems associated with fluidization, processing and fine particle deposition, particularly 10 microns or less, can be alleviated or avoided, while other problems associated with uneven or premature formation can be alleviated electrostatic charge on particles of powdered material. The effect that can be achieved in individual cases will depend primarily on the following parameters:

(1) the nature of the ingredients;

(2) the amount of ingredients in the powdered material; and

3) particle diameter of the components of the powdered material.

Typically, the powder coating material of the present invention comprises at least 20% by volume of particles having a diameter of less than 10 microns, the weight fraction of such particles being at least 30, 40 or 50% by weight, even higher content of such particles being used. means at least 60, 70, 80, 90 or even 100% by weight as a limit. Powder coating materials with this particle distribution can be obtained by conventional grinding, but grinding in a high energy mill is a preferred method for producing such materials.

-2GB 287721 B6

The particle size distribution parameters of the powdered coating material can be measured by a number of methods that can give a fraction of particles with a given range in diameter, volume or number of particles in this range, and the like. Data relating to the mass or volume of particles within a certain range are very commonly used, and it is apparent that for a given powder material, the weight fraction or bulk fraction within a given range is equivalent to that given that the material has a constant density. Volume-based distribution will be reported during the application. This distribution can be determined by a variety of laser-based devices, such as Cis-1 (Galia), Helos (Sympatec), or Mastersizer X (Malvem), but preferred examples of such devices are given, but any comparable device can be used.

In the powder coating compositions of the invention, at least 95% by volume particles, preferably at least 99% by volume particles have a diameter of less than 50 microns. Preferably, substantially all particles can meet this requirement. In preferred embodiments, at least one, preferably a plurality of, the following particle diameter requirements are met:

(a) 95 to 100% vol. <50 micrometers.

(b) 45 to 100% vol. <20 micrometers;

(c) 20 to 100% vol. <10 micrometers;

(d) 5 to 70% vol. <5 micrometers;

e) d (v) ₅₀ in the range of 1.3 to 20 microns, wherein d (v) ₅ % is a particle diameter value below which the diameter of 50% by volume of the particles in the mixture lies.

In particularly preferred materials, all of the requirements a) to e) are met.

Materials having the following particle size distribution on a volume basis may also be mentioned:

> 95% or> 99% or 100% <45 micrometers <45 micrometers <45 micrometers <40 micrometers <40 micrometers <40 micrometers <35 micrometers <35 micrometers <35 micrometers <30 micrometers <30 micrometers <30 micrometers <25 micrometers <25 micrometers <25 micrometers <20 micrometers <20 micrometers <20 micrometers <15 micrometers <15 micrometers <15 micrometers <10 micrometers <10 micrometers <10 micrometers

The ability to process and apply very fine particulate powder materials, i.e., a high proportion of particles having a diameter of 10 microns or less, also provides the ability to apply relatively thin coatings of 30 microns or less at uniform opacity and at least as good as normal appearance. coatings applied in the same way at a thickness of 50 to 60 microns.

A further surprising advantage which can be obtained with the powder materials according to the invention is that, when powdered materials are used for the formation of very fine particle coatings, a very good surface appearance of the formed coating can be achieved after curing. This good appearance can be obtained especially when at least 50% by volume of the powdered material has a particle size of less than 10 microns and at least 99% by volume of the material has a particle diameter of less than 20 microns, in which case there is almost no irregularity in appearance. and at the same time has the coating obtained

-3GB 287721 B6 High gloss and object mirroring. The absence of irregularities can be confirmed by measuring the surface of the profile and determining the conventional surface roughness quotient, as further described in the Examples section of the application.

An improved appearance of the coating surface can be obtained at a film thickness of 30 microns, but can be achieved even at a thickness of only 15 or even 10 microns. Film thicknesses below 15 microns may cause opacity problems for some colors, especially white. Coatings with a thickness of less than 10 microns are rarely used for decorative purposes, for example in the coating of canned food. In this case, non-pigmented coatings of the order of film thicknesses of 5 microns or less are also used. Such films can also be achieved using the powder material of the present invention.

The fine particle coating compositions of the present invention may also be applied to achieve good coating surface appearance even with relatively thick film layers, for example 50 microns or more, for example up to 80 or 90 microns. It should be noted, however, that there is generally a greater risk of cracking in the film at a greater film thickness, probably based on reverse ionization.

Grain-free coatings can also be achieved using the powder coating compositions of the present invention. If the maximum particle diameter of the material is more or less close to the desired film thickness, the formation of grains that could arise from errors during extrusion or milling can be prevented. For example, if it is desired to form a film free of grain at a thickness of 30 to 35 microns, the powder coating material must be ground so that 100% of the particles have a diameter of less than 35 microns.

There is also the possibility of obtaining a third color in the coating by electrostatic spraying using a powder material containing particles with two or more different colors. GB 2 226 824A (EP 0372860A) discloses that by mixing two or more differently colored powder materials with a sufficiently small particle diameter, for example, such a particle size distribution that substantially all particles have a maximum dimension below 10 microns it is possible to obtain a coloring of the powdered material which is different from that of the two components. The patent also teaches that individual powder coatings having a particle size distribution such that substantially all particles have a diameter of less than 10 microns, and mixtures of such materials are not normally fluidizable in air and in particular cannot be applied by conventional electrostatic spraying equipment. Therefore, it is proposed that the particles can be agglomerated to produce a powder material with altered particle size distribution in favor of larger particles so that the materials obtained can be sprayed in air and in particular such materials can be applied using commercially available electrostatic spray devices.

According to one embodiment of the invention, very fine powder coating materials can be prepared in which substantially all of the particles have a largest dimension of less than 10 microns so that the materials can be atomized in air. A surprising further advantage which can be obtained according to the invention is that when mixtures of two or more differently colored powder materials with very fine particles are prepared, they are not only sprayable in air but can be applied. using commercially available electrostatic spray devices to form a film which will be perceived as a film with a homogeneous color without perception of the individual components of the color and without electrostatic separation of the individual color components. In addition, the resulting film has a very good surface appearance.

The additive used in the powder materials of the invention may be a second group metal compound, for example calcium oxide, a twelfth group metal compound, for example zinc oxide, a transition metal compound such as Group 4 metal such as zirconium or hafnium, or a metal compound from group 6, for example molybdenum oxide or tungsten oxide, a metal compound of group 13, such as aluminum oxide or aluminum hydroxide, and

Β-block metal or metalloid, for example from group 14, such as silica or else a rare earth metal compound, such as lanthanum or cerium oxide.

The additive from the group of oxides may be an oxide of an element of a basic nature, for example calcium oxide or an oxide of an amphoteric element such as alumina or zinc oxide.

The additive from the group of oxygen salts may be a silicate, such as aluminum silicate, borate, phosphate, for example magnesium phosphate, carbonate, such as magnesium carbonate or sulfate.

In the case of an additive which is an oxide, oxide-hydroxides or aluminum hydroxides is probably possible to use any of the main structural types, i.e. alpha-ABCE corundum .alpha.-AlO (OH) Diaspore .alpha.-Al (OH) ₃ Bayerite gamma-Al ₃ O ₃ gamma-AlO (OH) boehmite gamma-AlO (OH) ₃ gibsit.

The silica is preferably annealed silica.

Preferred combinations of additives for use in the powder materials of the invention may be, for example, the following combinations:

(A) an additive selected from the group consisting of alumina, aluminum hydroxide, calcium oxide, silica, zinc oxide, zirconium oxide, molybdenum oxide, cerium oxide, and tungsten oxide, preferably alumina or silica, especially alumina; and

B) an additive selected from aluminum hydroxide, aluminum silicate, zirconium oxide, zinc oxide, silica and calcium oxide, preferably aluminum hydroxide.

It is anticipated that most combinations of ingredients selected from the above groups A) and B) will be effective in all cases of use in the powder materials of the invention, but combinations in which molybdenum oxide, cerium oxide or tungsten oxide are used as the sole component of groups A) will generally be somewhat less suitable, especially in the case of a higher content of particles with a diameter of less than 10 microns, and there may be a case towards the lower end of the range where the effect of an additive is too small to be considered significant .

In a preferred embodiment, one of the additives is alumina in any combinations of the invention.

A particularly preferred combination of additives according to the invention is composed of aluminum oxide and aluminum hydroxide. Another preferred combination is alumina and aluminum silicate.

Preferably, the at least one additive to be added by dry blending is an oxide or a mixed oxide. Preferred combinations of additives include an oxide or mixed oxide with another oxide or mixed oxide, hydroxide or oxide hydroxide. In these preferred additive combinations, each additive may be selected from those mentioned above.

-5GB 287721 B6

It is also possible to use more than two dry mixing ingredients. Thus, according to the invention, for example, two or more of the group B additives as mentioned above may be added together with the group A additive. Preferably, however, the material of the invention contains only two dry mixing additives.

The total amount of such additives in the powder coating composition of the present invention will generally be in the range of 0.01 to 10% by weight based on the weight of the additive-free material, preferably at least 0.05 and especially at least 1.0% by weight. In principle, more than 10% by weight of additives can also be used, but the use of larger amounts will adversely affect the surface appearance of the coating thus obtained.

In the case where one of the additives to be added by dry mixing is alumina, the proportion of this oxide is at least 0.01% by weight, based on the weight of the material without additives, preferably at least 0.02 and in particular 0.2-0.4% % by weight. Due to the relatively strong effect of this substance on electrostatic phenomena, the proportion of alumina will normally not be higher than 1% by weight, but under certain circumstances higher amounts may be used, for example for a material with a very wide particle size distribution or a mixture of two powdered substances, one of which is composed of particles having substantially all diameters less than 10 microns and the other having substantially coarser particles. In such circumstances, the proportion of alumina may be, for example, up to 2.5 or even 5% by weight. In principle, up to 10% by weight of alumina can be used, but the higher the amount, the greater the adverse effect on the surface appearance of the finished coating.

In general, for a given amount of powder coating material, it is likely that the amount of each additive required to achieve a certain effect will be the smaller the particle size of the material, given that the amount of additive required for that amount the powdered material probably depends on the number of particles in the material.

Typically, where one of the additives used is alumina, the content of the other additive or additives, for example from the above group B, will usually not exceed 5% by weight based on the total weight of the material without additives and usually will not exceed 3% by weight. exceed 1% by weight, based on the amount of material without additives. An example of a preferred additive combination is 0.36% alumina and 2.64% alumina.

In cases where no alumina is used as an additive, i.e. another additive has been used from Group A above, the total additive content of the coating material will usually be higher than if one of the additives is alumina and typically, it may be in the range of 0.5 to 15% by weight, with the content of each individual additive in the range of 0.1 to 14.9% by weight.

In preferred cases of using two additives, the relative proportions of these additives may be in the range of 1: 99 to 99: 1, typically (except in cases where one of the ingredients is alumina) in the range of 40: 60 to 60: 40. For example, the ingredients of the group A and B above may be from 10 to 40% by weight of the Group A component and from 60% to 90% by weight of the total ingredients of the Group B component.

Although the particle size of each of the dry mixing ingredients may be up to 5 or in some cases up to 10 microns, preferably this particle size is not more than 2 microns and in particularly preferred cases is at most 1 microns. In general, the lower the coating thickness, the smaller the additive particles to be used.

The additives used according to the invention are added to the powder coating material by dry mixing after the powdered material has been produced. It is very advantageous that the additives used are premixed, preferably very thoroughly and homogeneously, and then only be mixed

However, in principle, it is also possible to add the individual ingredients separately by dry mixing.

In principle, the additive combination according to the invention can also be added by adding one additive coated with the other additive. Thus, for example, it is possible to add an oxide, for example alumina, which is coated with another oxide or hydrated oxide or hydroxide, for example hydrated zirconia, hydrated silica or aluminum hydroxide. Such a coating may be formed by known methods, for example by precipitation or evaporation of the solvent from solution. A single coating or multiple coatings may be deposited.

The powder coating material of the present invention may consist of a single powder coating component which may comprise a film-forming polymer, a curing agent and optionally one or more colored components, or the powder material may be a mixture of two or more such components.

This component or any such component of the powdered material according to the invention will generally be a thermosetting plastic system, although thermoplastic systems, for example based on polyamides, may also be used.

The film-forming polymer used in the manufacture of each of the thermosetting plastics powder coating components of the present invention may be selected from, for example, polyester carboxyl or hydroxyl functional resins, epoxy resins and acrylic functional resins.

For example, the component of the powdered material may be selected based on a solid polymeric binder system comprising a carboxyl-functional polyester film-forming resin, the polyepoxide being used as the curing agent. Such carboxyl-based polyester systems are currently the most widely used powder coating materials. The polyester typically has an acid number in the range of 10 to 100, a number average molecular weight Mn in the range of 1500 to 10,000 and a glass transition temperature Tg in the range of 30 to 85, preferably at least 40 ° C. For example, the epoxide or polyepoxide may be a low molecular weight epoxy compound such as triplycidyl isocyanurate, TGIC, diglycidyl terephthalate or diglycidyl isophthalate, or an epoxy resin such as condensed glycidyl ether of bisphenol A, or may be a light-stable epoxy resin. Such a carboxyl-functional polyester film-forming resin can be used with bis-betahydroxyalkylamide as hardeners, for example tetrakis (2-hydroxyethyl) adipamide.

It is also possible to use a hydroxyl-functional polyester using a hardened isocyanate-functional material or an amine-formaldehyde condensate such as a melamine resin, a urea-formaldehyde resin or a glycol-formaldehyde resin as marketed under the trade name Powderlink 1174 (Cyanamid Company). or hexahydroxymethylmelamine. The isocyanate-blocked hardener for the hydroxyl-functional polyester may be, for example, an intrinsically blocked substance, such as a zuretdione, or may be a caprolactam-type substance, for example isopherone diisocyanate.

As an alternative, an epoxy resin may be used together with an amine-functional hardener, for example a dicyandiamide sol. Instead of an amine-functional hardener, phenol type materials may be used for epoxy resins, preferably a material formed by reacting epichlorohydrin with an excess of bisphenol A (i.e. polyphenol formed by the addition of bisphenol A and epoxy resin). It is also possible to use resins with functional acrylic groups, for example with carboxylic, hydroxyl or epoxy functional groups, together with an appropriate hardener. Mixtures of binders may be used, for example, carboxyl-functional polyester may be used together with acrylic

A carboxyl-functional resin and a hardener, for example bis-beta-hydroxyalkylamide, which cures both polymers. Another possibility is to use a mixture of binders, for example an acrylic resin with carboxyl, hydroxyl or epoxy groups can be used together with an epoxy or polyester resin with carboxyl or hydroxyl functional groups. These resin combinations can be selected to cure one another, for example, a carboxyl-functional acrylic resin together with an epoxy resin or a carboxyl-functional polyester together with a glycidyl-functional acrylic resin. Usually, however, mixtures which can be cured with a single hardener can be used, for example, a blocked isocyanate can be used to cure a hydroxyl-functional acrylic resin and a hydroxyl-functional polyester. In another preferred embodiment, a different hardener may be used for each of the two polymeric materials, for example, an amine cured epoxy resin together with a blocked isocyanate cured acrylic resin.

Other film-forming polymers may also be mentioned, for example, fluorine-functional polymers, fluorinated and chlorinated polymers and fluoroacrylic polymers, these polymers may also contain hydroxyl or carboxyl functional groups and may be used as the sole film-forming polymers or in conjunction with one or more acrylic, polyester and / or epoxy resins using appropriate hardeners for each of said polymers.

Other curing agents include epoxyphenol novolaks and epoxycresol novolaks, oxime blocked isocyanate hardeners, e.g. (Monsanto) and alicyclic polyepoxides such as EHPE-3150 (Daicel).

The powder coating component of the invention may be free of color materials, but usually contains one or more such materials, for example pigments or dyes, and may additionally contain one or more other ingredients to achieve the desired effect as a flow aid, a plasticizer, a stabilizer, for example a stabilizer against degradation by ultraviolet light, a gas inhibiting agent such as benzoin, a filler, or two or more of such coating additives may be used. Examples of pigments that can be used are inorganic pigments such as titanium dioxide, red and yellow iron oxide, chromium-based pigments, carbon black and also organic pigments, for example talocyanines, azo dyes, anthraquinones, thioindigo, isodibenzanthrone, trofendioxan and pigments based quinacridone, leak dyes, acid or base paints and mordants. Dyes can also be used instead of pigments.

The pigment content may comprise less than 40% by weight of the total weight of the material without additives, added by dry mixing. Usually 25 to 30% by weight of pigment is used, although in the case of dark colors opacity can be achieved even at less than 10% by weight of pigment. If necessary, a filler may be used to increase opacity for reasons of economy.

Although materials that are colored may be used as dry additive materials to the present invention, it is not usually desirable that these additives change the color of the material, since the color of these materials is usually determined by the addition of color components that are usually added. prior to processing the material into a powder form.

Another object of the present invention is to provide a method of coating substrates, the method comprising depositing an electrostatic spray on a substrate according to the present invention and then heating the material to melt and melt the particles to cure the coating.

-8EN 287721 B6

In electrostatic spraying, it is possible to use particle charging by means of a corona discharge or by means of turbo-electric phenomena. In the case of triboelectric phenomena, it is completed that the powdered material has already been processed with respect to this use, for example by selecting suitable polymers known to be safe for this purpose, or by using suitable additives which can be added in a known manner prior to use. by extruding the material.

The present invention also provides a substrate coated by the process of the present invention, preferably having a thickness of 30 microns or less.

The substrate may be metal, heat-resistant plastic, wood, glass, ceramic or textile material. Preferably, the metal substrate is chemically or mechanically cleaned prior to depositing the material and is preferably pre-treated, for example, by treatment with iron phosphate, zinc phosphate or chromate. Substrates other than metal substrates are generally preheated or pretreated prior to application using materials that facilitate electrostatic deposition.

The following examples illustrate the use of additives added to the material of the invention by dry blending.

In determining the appearance of the films formed from the powdered materials according to the invention, and in particular in detecting defects in the appearance of the orange skin, it is appropriate to use graphical data obtained profilometrically on the cured coated films. By way of example, these tests were performed using a UB16 type laser profilometer (Ulrich Breitmeier Messtechnik GMBH, UBM). Light from the semiconductor laser in the sensor is applied to the surface to be monitored in the form of a focus. The movable lens suspended in the sensor is continuously adjusted so that the focus of the rays is always deposited on the surface of the film. The sensor is designed such that any roughness on the surface of the coating causes movement of said lens which is detected by the second measuring system.

The resulting data are shown graphically in the attached drawings.

Overview of the drawings

FIG. 1 shows, for comparison, the results of a profilometric analysis of a 50 micron thick film produced using a coating material of conventional particle size.

Figure 2 shows the results of profilometry on a cured film having a thickness of 55 microns; the film was formed using the powder material of Example 1, a powder material with more favorable properties than the film of Figure 1.

Fig. 3 shows the results of the profilometry of the cured film with a micrometer thickness using the "standard" powder described in Example 1.

Fig. 4 shows the results of the profilometry of a cured film having a micrometer thickness according to the invention, using the "standard" powder of Example 1 after reducing the particle size and adding the additive mixture according to the invention.

Fig. 5 shows the results of profilometry on a cured film having a micrometer thickness, the film being formed using the "standard" powder of Example 2.

Fig. 6 shows the profilometry results of a cured film with a micrometer thickness, the film being produced according to the invention using a "standard"

The powder of Example 2 after reducing the particle size and adding the additive mixture of the invention.

Figure 7 shows the results of the profilometry of a cured film having a thickness of 25 microns, the film being formed using the powdered material of the invention described in Example 6.

Figures 8, 9 and 10 graphically show data from Experiments I and III below.

Referring to Figures 1 to 7, this is a graphical representation of surface defects of the orange skin appearance type. The higher the amplitude and the shorter the wavelength of the series of peaks, the more pronounced the defect is.

The film shown in FIG. 1 has a very non-aesthetic surface appearance.

A large difference in comparison with such a surface can be observed, for example, in Figure 6, where it is apparent that there is almost no deviation from the baseline, which means that the surface defect is almost absent. Data for the amplitude caused by this defect can be converted to a roughness expressed in micrometers and referred to as the so-called roughness quotient Rq. Obviously, in Figure 1, which results for the worst surface, this quotient is 1.89 microns, while in the case of Figure 6, which is shown for the best surface, the quotient is 0.086 microns. Thus, it is clear that the lower the quotient, the better the surface. The vertical axis in each drawing shows the surface profile in micrometers. The horizontal axis is scaled in millimeters.

The aluminum oxide used in the Example was Aluminum Oxide C (Degussa), with a mean particle diameter of less than 0.2 microns. The aluminum hydroxide used was Martinal OL107 (Croxton and Garry) with a mean particle diameter of 0.9 to 1.3 microns and the aluminum silicate used was aluminum silicate P820 (Degussa) with a mean particle diameter of less than 0.1 micrometer.

The composition of the individual additive combinations to be added by dry blending will be described below.

Combination 1

Aluminum oxide120 g aluminum hydroxide880 g

The ingredients are added to a high shear mixer (Moulinex), mixed for 60 seconds and retained for future use.

Combination 2

Aluminum oxide350 g Aluminum hydroxide650 g

The ingredients are placed in a high shear mixer (Moulinex) where they are mixed for 60 seconds and then stored for future use.

-10GB 287721 B6

Combination 3

Aluminum oxide 500 g Aluminum silicate 500 g

The ingredients are placed in a high shear mixer (Moulinex) where they are mixed for 60 seconds and then stored for future use.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

White powder coating material

Rutile (titanium dioxide) as a white pigment 250 g black iron oxide 306 ig ultramarine blue No. 17 1 g filler (barite) 150 g polyester resin with functional carboxyl groups 372 g epoxy resin as hardener 164 g Laropal A81 aldehyde resin 50 g catalyst ig flow modifier 5g benzoin 3g polyethylene wax Ls

The ingredients are mixed in a mixer and then fed to a twin screw extruder operating at 108 ° C. The extruded material is milled in an impact mill to form a powder with the following particle size distribution.

100% <103 micrometers 30% <20 micrometers 10% <10 micrometers 3% <5 micrometers D (v) ₅₀ 30.9 micrometers.

The flow index of this "standard" powder was measured with a SAMES AS 100 and found 39.3.

A portion of the material was then electrostatically sprayed onto steel panels to produce cured films having a thickness of 55 and 30 microns (in both cases, the coatings were cured by heating to 180 ° C for 15 minutes). Both panels had a 88% gloss at 60 °. A laser profilometer was used to evaluate the film surface. Roughness quotients of 0.55 microns for a film having a thickness of 55 microns and 0.83 microns for a film with a thickness of 30 microns were found. Both results are shown graphically in Figures 2 and 3.

Each of these coatings, formed from a "standard" powder with a gel formation time of 80 seconds at 200 ° C, had a Gardener impact resistance of 10 J (both front and back) and a score of 5.0 mm in the erichsen formation .

- 11 CZ 287721 B6

Another portion of the powder was further processed in an Alpine jet mill (400AFG) to reduce the particle size. The mill speed was adjusted until the maximum particle size formed was nominally 35 microns. The particle size distribution of the resulting powder was as follows:

99% <50 micrometers 72% <20 micrometers 35% <10 micrometers 10% <5 micrometers D 13.9 micrometers

The material with such reduced particles was then mixed with 0.8% by weight combination of 2 additives. The resulting material was then sprayed onto a steel panel to form a 30 micron thick film. The surface quality of this film was then determined and the roughness quotient was shown to be 0.31 micrometers (Fig. 4).

the same material was then applied under the same conditions as above to the aluminum substrate to form a film with a thickness of 80 to 85 microns, on whose surface no apparent defects could be observed despite the large film thickness. The roughness quotient value in this case was 0.17 micrometer.

The gel formation time and the physical and mechanical properties of the thus formed film were the same as those of the standard powder.

In another experiment, a sample of reduced particle size powder material at low shear was mixed with 0.75% by weight of a combination of 3 ingredients. The resulting material, including the additive, was then sprayed onto a steel panel to form a 30 micron thick film. The Rq of the cured film was 0.32 microns. This is a similar result to that achieved with the combination of 2 ingredients.

In another experiment, the material was produced as above, except that the impact mill was equipped with a double cyclone in which fine particles were accumulated. Using this arrangement, finer particles likely to escape from the primary cyclone are retained in the secondary cyclone. The impact mill (Hosokawa ACM30) was set to produce the smallest possible particle size (2600 rpm, 26 m ³ / min air flow). The fine particles were trapped in a secondary cyclone and the following particle size distribution of the material was achieved:

100% 35 micrometers 97% 20 micrometers 75% 10 micrometers 32% 5 micrometers D (v) ₅₀ 6.7 micrometers.

The flow index for the resulting fine powder (without additives according to the invention) was measured using an AS 100 and was only 2.1 compared to 39.3 for a powder of the "standard" type.

This fine powder was mixed with 1.0% by weight of the combination of 2 ingredients of the invention. The flow index of the resultant coating material of the present invention as measured by the same apparatus was 109 compared to only 2.1 for the small particle powder without additives of the invention. The resulting additive material was then sprayed onto a steel panel to form a 30 micron thick film. The surface quality of this film was determined, the measured roughness quotient being 0.17 microns.

- 12GB 287721 B6

The gel formation time for this powdered material and the mechanical properties of the obtained film were the same as for the standard known material.

Example 2

Material for making thin film

Rutile (titanium dioxide) as a white pigment 190 g Bayferrox 3g blue pigment Helicosin 5g carbon black 2g filler (dolomite) 60 g filler (barite) 80 g Bisphenol-A-epoxy resin 533 g SMA 1440 resin (styrene / maleic anhydride) 90 g amine as a hardener 28 g flow modifier 6g benzoin 2g

The ingredients were dry blended and fed to an extruder operating at 90 ° C. The extruded material was ground in an impact mill to produce a "standard" particle size distribution powder:

100% <98 micrometers 33% <20 micrometers 11% <10 micrometers 3% <5 micrometers D 28 micrometers.

This powdered material was electrostatically sprayed onto an aluminum panel to form a 20 micron thick film, cured at 140 ° C for 15 minutes. The film surface was examined by a laser profilometer, the roughness quotient being 1.31 micrometers (Fig. 5).

The powdered material was then further treated with an impact jet mill using air to further reduce the particle size. The following particle size distribution of the resulting powder was achieved:

99% <10 micrometers 47% <5 micrometers D (v) ₅₀ 5.1 micrometers.

The fine powder was then mixed with 1.1% combination of 1 ingredients and sprayed onto an aluminum panel to form a 20 micron thick film, cured at 140 ° C. The surface of the film was examined by a laser profilometer, and the roughness quoted was 0.09 microns, as also shown in Figure 6.

- 13GB 287721 B6

The panels coated with the method of Example 2 were then compared using a series of tests.

exam test results standard powder powder with smaller particles impact toughness satisfactory satisfactory adhesion of dry and wet material satisfactory satisfactory salt spray resistance (1000 h) satisfactory satisfactory reticulated corrosion resistance (1000 h) compliant (1.5 mm) compliant (1.5 mm)

Examples of color mixing

The base materials in the form of colored powders were prepared as individual compositions with the following composition.

Materials containing polyester and epoxy

Basic material of white color

Rutile (titanium dioxide) as a white pigment 313 g filler (dolomite) 7g a polyester resin with carboxyl functional groups ⁴⁷³ S epoxy resin as hardener 190 g catalyst 2g flow modifier 7g benzoin 3g polyethylene wax _

The ingredients were dry blended in a mixer and then placed in a double screw extruder operating at 108 ° C. The extruded material was ground in a shock mill to a powder which contained 100% particles with a size of less than 180 microns.

The particle size of this powder was then further reduced in an Alpine 400 AFG jet mill to obtain a powder with the following particle size distribution:

100% <12 micrometers 95% <10 micrometers 55% <5 micrometers D (v) ₅₀ 3.6 micrometers.

Further, a blue base powder having the following composition was prepared:

- 14GB 287721 B6

Blue powder base

Cl blue 60 as pigment 49 g filler (barite) 30 g filler (dolomite) 30 g a polyester resin with carboxyl functional groups 642 g epoxy resin as hardener 234 g catalyst 2g flow modifier Tg benzoin 3g polyethylene wax 3g

The ingredients were dry blended in a mixer and fed to a double screw extruder operating at 108 ° C. The extruded material was ground in an impact mill to produce a powder with 100% particles smaller than 180 microns.

The particles of this powder were further reduced in a jet mill using air (Alpine 400 AFG) to produce a powder with the following particle size distribution:

100% <12 micrometers 93% <10 micrometers 54% <5 micrometers D (v) ₅₀ 3.9 micrometers.

Red powder base

Cl 170 Novoper, as a red pigment 78 g filler (barite) 52 g filler (dolomite) 52 g polyester resin with carboxyl functional groups 564 g epoxy resin as hardener 237 g catalyst 2g flow modifier 8g benzoin 3g polyethylene wax lg

The ingredients are dry blended in a mixer and then fed to a twin-screw extruder operating at 103 ° C. The extruded material is milled in an impact mill to produce a powder having 100% of the particles having a diameter of less than 180 microns.

This powder is then further processed in a jet mill using air (Alpine 400 AFC) to give a powder with the following particle size distribution.

100% <8 micrometers 60% <5 micrometers D (v) ₅₀ 3.1 micrometers

Example 3

Powder coating material A, light blue (comparative)

- 15GB 287721 B6

White powder base material 500 g Blue powder base material 500 g

The base powder materials were placed in a high shear mixer (Moulinex) and blended for 10 seconds to form a mixture with a flow index O (Sames AS 100). The powder mixture was then sprayed at -30 kV and -70 kV using a spray gun (Ransberg Gema PG1) on two separate aluminum panels. Spraying was very difficult due to the small particle size, thus blocking and accumulating powder material in the gun.

The coated panels were heated at 200 ° C for 15 minutes. Both panels were then analyzed for color differences using a spectrophotometer (Macbeth MS 2020) and an ICS color counter.

It was shown that the color difference of both panels, deltaE (light D65) = 6.7.

Powder coating material B, light blue (according to the invention)

White powder base material 500 g Blue powder base material 500 g Combination of 1 ingredients10 g

The dry blended base materials and additives of the invention were placed in a high shear mixer (Moulinex) and blended for 10 seconds. The resulting powder mix with a flow index of 51 (Sames AS 100) was then sprayed at -30 kV and -70 kV using a gun (Ransberg PG1) on two separate aluminum panels. In this case, there was no difficulty in spraying.

The coated panels were heated to 200 ° C for 15 minutes. The panels were then analyzed to determine color difference using a spectrophotometer (Macbeth MS 2020) and an ICS color counter.

It was shown that the color difference of both deltaE panels (light D65) - 0.3.

Example 4

Material A Magenta (Comparative)

White powder base material 400 g Blue powder base material 200 g Red powder base material 400 g

The base powder materials were placed in a low shear mixer (Kenwood) and mixed for 15 minutes. The material is then applied at -30 kV and -70 kV guns (Ransgerb Gema 701-6) to two separate steel panels. Spraying was very difficult due to the small particle size of the materials, so that the gun was blocked and the material accumulated in the gun.

-16GB 287721 B6

The coated panels were heated at 200 ° C for 15 minutes to form cured films having a thickness of 30 microns. Then, both panels were analyzed for color difference using a spectrophotometer (Macbeth MS 2020) and an ICS color counter.

It was shown that the color difference of both panels, deltaE (light D 65) = 3.35.

Material B purple (according to the invention)

White powder base 400g Blue powder base 200g Red powder base 400g Combination of 2 ingredients10 g

The basic powder materials and combinations of ingredients of the invention were placed in a mixer (Kenwood) and mixed for 15 minutes. The resulting powder mixture was then sprayed at 30 kV and -70 kV by spray gun (Ransberg Gema 701-6) onto two separate steel panels. In this case, the powder passed freely through the gun.

The coated panels were heated at 200 ° C for 15 minutes to form cured films having a thickness of 30 microns. Both panels were then analyzed for color difference using a spectrophotometer (Macbeth MS 2020) and an ICS color counter.

The color difference of both panels was shown as delta E (light D65) = 0.5.

Example 5

Red powder material (according to the invention)

White base material Red base material Combination of 2 ingredients

666 g

334 g g

The basic powder materials and combinations of ingredients of the invention were placed in a mixer (Kenwood) and mixed for 15 minutes. The powder mixture was then sprayed at 70 kV guns (Ransberg Gama 701-6) onto an aluminum panel. The powder passed freely through the gun.

The coated panel was heated to 200 ° C for 15 minutes to give a cured film of 12-15 micron thickness with very good film surface quality. Film surface quality was measured using a laser profilometer (UBM). In this test, a surface roughness quotient of 0.182 microns was determined.

Polyester / hydroxyalkylamide

- 17GB 287721 B6

Powder of blue color

Blue pigment Graphitol 33 g filler (barite) 87 g a polyester resin with carboxyl functional groups 826 g hydroxyalkylamide as a hardener 34 g flow modifier 14 g benzoin 3g kamauba wax Ls

The ingredients are dry blended and then fed to an extruder operating at 100 ° C. The extruded material is ground in a pulverizer to a powder in which 100% of the particles have a dimension of less than 180 microns.

This powder is then further processed in a jet mill using air to obtain a sample, followed by a particle size distribution (% by volume).

99.0% <10 micrometers 43.0% <5 micrometers D (v) _5o 5.5 micrometers.

Powder material of brick color

Pigment 130 BM based on red iron oxide 111 g filler (barite) 190 g a polyester resin with carboxyl functional groups 656 g hydroxyalkylamide as a hardener 27 g flow modifier 10 g benzoin 3g kamauba wax 3g

The ingredients are dry blended and then fed to an extruder operating at 140 ° C. The extruded material is ground in a pulverizer to a powder in which 100% of the particles have a dimension of less than 180 microns.

This powder is then further processed to reduce the particle size in the jet mill using air to give a powder with the following particle size distribution.

99% <10 micrometers 47% <5 micrometers D (v) ₅₀ 5.1 micrometers

- 18GB 287721 B6

White powder base

Rutile (titanium dioxide) as a white pigment 335 g filler (barite) 25 g a polyester resin with carboxyl functional groups 585 g hydroxyalkylamide as a hardener 25 g flow modifier 14 g benzoin 3g kamauba wax 3g

The ingredients are dry blended and then fed to an extruder operating at 140 ° C. The extruded material is milled in an impact mill to produce a powder in which 100% of the particles are less than 180 microns in size.

This powder is then further processed in a jet mill using air to form a powder with the following particle size distribution (% by volume).

100% <10 micrometers 44% <5 micrometers D (v) ₅₀ 5.3 micrometers

The flow index for all the mentioned types of base powders, blue paint, brick paint and white paint (fine powders without additives according to the invention) was 0 (Sames AS 100).

Example 6

Camomile blue powder material (according to the invention)

Base Powder Blue Color Base Powder White Color Base Powder Brick Color Combination of 2 ingredients

330 g

520 g

150 g g

The base powder materials are mixed in a Kenwood mixer for 15 minutes. The combination of ingredients of the invention is then added and the resulting mixture is further blended at low speed. The powder blend, including additives having a flow index of 84 (Sames AS 100), was then electrostatically sprayed onto an aluminum panel to form a 35 micron thick film. The coating was cured at 200 ° C for 10 minutes. The resulting coating had a homogeneous blue color with high gloss (90% at 60 °) at very good flow properties. The roughness quotient for this film was 0.124 micrometers (Fig. 7).

Example 7

Low-gloss powder coating material, cream paints for triboelectric charging

-19GB 287721 B6

Polyester resin with functional carboxyl groups 33,79% epoxy resin as hardener 27,12% benzoin 0.18% wax 0.54% charge control agent 0.36% catalyst 0.02% rutile (titanium dioxide) as a pigment 27,12% black iron oxide 0,03% red iron oxide 0.01% yellow iron oxide 0.14% filler 9.06% flow modifier 1,45%

The ingredients were dry blended in a mixer and fed to a double screw extruder operating at 108 ° C. The extruded material was ground in an impact mill and sieved to give a powder for comparison purposes in which 100% of the particles had a size of less than 10 6 microns.

A portion of the resulting cream colored material was then sprayed onto aluminum gun panels (Nordson ICAB) using a triboelectric charge, and then heated to 180 ° C for 15 minutes to cure the coating. The cured coatings had a thickness of 50 to 60 microns and a gloss of 26 to 28% (at 60 °).

Another portion of the cream colored powder material was then further processed to reduce the particle size in a jet mill (Alpine 100 AFG). The mill speed was adjusted until a nominal maximum particle size of 35 microns was reached. In this way 15 a powder was obtained with the following particle size distribution.

100% <36 micrometers 87% <20 micrometers 40% <10 micrometers D (v) _5o 12.1 micrometers.

The reduced particulate powder material is then mixed with a 1% by weight combination of 2 additives according to the invention at low shear. The resulting material was then sprayed onto an aluminum gun panel using triboelectric phenomena (Nordson ICAB) for 20 times to form a 30 micron thick film.

The surface quality of both films was compared using a laser profilometer. Obviously, the roughness quotient of such a system is a combination of two types of surface roughness. The first type 25 is caused by unevenness of the surface when it is made of powdered material, the second type is caused by intentional failure of the surface so that the surface has a matt appearance. Since the nature of the two types is very different, it was possible to separate the two types by a suitable program of the computer that controlled the profilometer. The following results were obtained:

standard film (comparative) thin film (according to the invention) look orange peel matt appearance (noise) look orange peel matt appearance (noise) Rq 1.41 0.36 0.29 0.34

The Rq values for the film formed from the standard reference powder show that the defects of the orange peel appearance are more pronounced than in Figure 2, but not as severe as the

Fig. 1. Rq values for powder processed to a smaller particle size at a film thickness of 30 microns demonstrate that the appearance is similar to that of Figure 4.

The gel formation and other physical and mechanical properties of the film according to the invention corresponded to the values obtained for the film obtained using standard material.

In addition, the values for the friction charge (C / M ratio) for standard powders and for powders with a smaller particle size were determined by placing a cartridge size measuring device between the gun ground and ground and simultaneously measuring the amount of powder material passing through gun in g / min. The following values were obtained:

standard powder (1.10 + 0.08) x 10 ³ C / kg powder with smaller particle size + combination of 2 additives (0.39 ± 0.04) x 10 ^-3 C / kg.

Example 8

Very free-flowing powder for full-gloss coating

Black No. 6 1.50% polyester resin with carboxyl functional groups 82.00% Primid XL552 3,40% an antioxidant 0.20% benzoin 0,40% silica to improve flowability 1.50% Blanc Fixe HD80 10,00% flow modifier 1.00%

The ingredients were dry blended and then fed to a single screw extruder operating at 130 ° C. The extruded material was ground in a shock mill to a coarser powder with the following particle size distribution.

100% <180 micrometers 25% <20 micrometers 8% <10 micrometers 3% <5 micrometers D (v) ₅₀ 8 micrometers

This powder was then further processed to reduce the particle size in a jet mill (Alpine 100 AFG) to form a powder with a subsequent particle size distribution.

100% <23 micrometers 68% <10 micrometers 23% <5 micrometers D (v) ₅₀ 8 micrometers

The smaller particle powder was then dry blended at low shear with 1.0% of the combination of 2 ingredients of the invention and the resulting material of the invention was sprayed using an electrostatic gun (Gema-Volstatic MPS 1-L) on aluminum panels to form 50 to 60 microns thick film and cured for 15 minutes at 200 ° C. This film was followed by a laser profilometer and had an Rq of 0.24.

-21 CZ 287721 B6

In addition, some of the raw powder after milling in a jet mill was also mixed at low shear with a 1% combination of 3 ingredients of the invention and the material of the invention so obtained was sprayed in the same manner as above to obtain a cured film 50-60 microns thick. The film surface was monitored using a laser profilometer and the Rq value was 0.25.

Example 9

Very thin film

polyester resin with hydroxyl functional groups 93.37% Powderlink 1174 4.83% catalyst 0,40% benzoin 0.20% a flow aid 1.20%.

The ingredients were dry blended in a mixer and then fed to an extruder operating at 110 ° C. The extruded material was ground in an impact mill to obtain a powder in which 100% of the particles were less than 200 microns in size.

This powder was then further processed to reduce particle size using a jet mill (Alpine 100AFG). The velocity was adjusted to obtain a product in which nominally 100% of the particles were less than 15 microns in size. The following particle size distribution was achieved.

100% <14 micrometers 93% <10 micrometers 43% <5 micrometers D (v) ₅₀ 6.1 micrometers.

The reduced particle size powder was then mixed at a low shear with 1.0% by weight of the combination of 2 ingredients of the invention. The resulting material was then sprayed using an electrostatic gun (Gema-Volstatic MPS 1-L) on aluminum panels to obtain a film having a thickness of 4 to 6 microns, after curing for 15 minutes at 180 ° C the films had a homogeneous appearance. The coated panels were then immersed in an acidified copper sulfate solution for 45 seconds to demonstrate film continuity. No difference could be detected between the part of the film immersed in the solution and the dry part of the panel, which means that the film was continuous without porous spots or small openings through which the acidic copper sulphate solution could penetrate to the metal substrate.

Testing of additive efficiency

In the following experiments I, II and V to VII the individual materials were evaluated for suitability for use as an additive according to the invention, in experiments III, IV, VIII and IX the use of different combinations of additives according to the invention was reported.

In experiments I to IV, color analysis was not performed on the cured films. Coloring analysis was performed on noncured corona discharge powdered materials on 7x5 cm aluminum plates. These plates were sprayed until the substrate was completely covered and then a microscope slide was placed on the sample to protect the powder coating. Staining analysis was performed through this slide using a spectrophotometer. In all

-22EN 287721 B6 cases, a standard sample was obtained by spraying at -70 kV, and color analysis was used to identify the color of the sample applied at -30 kV compared to the sample applied at -70 kV,

Further analysis was carried out by turning off the applied stress applied to the coated plates and the powder mixture separately on the aluminum plates at +20 kV and -20 kV. Each 7 x 5 cm aluminum plate was connected to a voltage source (Brandenburf Alpha III DC).

In experiments V-IX, color analysis was performed on heat-cured films.

The procedures used in experiments I to IX are conventional procedures for evaluating materials for use as additives and for evaluating combinations of additives, and the results of these tests form part of the invention. Obviously, the details of these processes, such as the size and type of plates, the applied voltage, mixing times and the like, may differ from those described during the application. In principle, however, the above procedures are generally well suited for determining the applicability of additives and in principle it is sufficient to make only comparisons at -70 and -30 kV, and there is no longer any need to perform comparisons at zero voltage and at ± 20 kV.

The following powder materials were used in experiments I to IX:

Red powder base material

red pigment 170 78 g filler (barite) 60 g polyester resin with functional carboxyl groups 791 g epoxy hardener 59 g flow modifier 6g benzoin 3g kamauba wax Ls

The ingredients are dry blended and fed to a single screw extruder (Buss PR 46) operating at 140 ° C. The extruded material was ground in an impact mill to give a powder in which 100%. the particle size was less than 180 microns.

This powder was then further processed in a jet mill using air (Alpine 400 AFG) to produce a powder with subsequent particle distribution (% by volume).

100% <11 micrometers 68% <5 micrometers D 4.3 micrometers

Base powder material based on blue polyester

Blue pigment Monolitet 3R 50 g filler (barite) 91 g a polyester resin with carboxyl functional groups 778 g epoxy hardener 60 g flow modifier 15 g benzoin 3g kamauba wax 3g

-23GB 287721 B6

The ingredients are dry blended and fed to a single screw extruder (Buss RP46) operating at 140 ° C. The extruded material is milled in an impact mill to produce a powder in which 100% of the particles are less than 180 microns in size.

This powder is then further processed to reduce particle size in a jet mill using air (Alpine 400 AGF) to form a powder with subsequent particle size distribution.

100% <8 micrometers 72% <5 micrometers D (v) ₅₀ 4.3 micrometers

Experiment 1 parts of the basic polyester powder of red color is mixed with 50 parts of polyester powder of blue color and mixed for 10 seconds in a blender (Moulinex). The mixture is then electrostatically sprayed at -30 kV and -70 kV onto aluminum plates. Spraying was very difficult due to gun blocking and material accumulation in the gun. The color difference of both plates was deltaE (D65) = 5.01. DeltaA (D65) - 3.52 (redder).

The same powder mixture was also sprayed on individual aluminum plate electrodes at +20 and -20 kV, in which case the color difference of both deltaE plates (D65) = 13.15. Delta A (D65) = 7.69 (redder).

In order to evaluate the effect of the alumina additive, a mixture of powder materials was formed as above and different amounts of alumina C were added to each sample. Each sample was then sprayed at -30 kV and -70 kV. Samples were also sprayed without voltage to aluminum plate electrodes at ± 20 kV. The differences in coloring of the resulting coatings are shown in Table 1 below.

Table 1

content A1 ₂ O ₃ board -30kV compared to -70kV + VE electrode compared to -EV electrode delta (D65) deltaA delta (D65) deltaA 0.0% 5.01 redder 3.52 13.15 redder 7.69 0.05% 3,07 redder 2.02 9.84 redder 7.13 0.1% 0.84 bluer -0.38 2.04 bluer -0.94 0.2% 2.48 bluer -1.56 6.75 bluer ^ 1.05 0.3% 2.73 bluer -1.35 9.48 bluer -5.57 0.6% 2.74 bluer -1.70 6.96 bluer -4.18 1.0% 1.95 bluer -1.30 4.30 bluer -2.18 2.5% 1.94 bluer -0.31 1.09 bluer -0.31

The plate electrodes reflect the positive and negative nature of the components of the powder mixture, the charges resulting from the spontaneous charging of the components by friction. In the absence of alumina, the blue colored polyester is deposited on the negative electrode, which means that it has a positive charge due to friction with the red polyester. The red-colored polyester, on the other hand, is deposited on the + ve electrode, which means that it is charged with a negative charge by friction. This behavior of the individual materials is also reflected when spraying at different voltages, where, in the absence of additives, negatively charged red powder particles are preferably deposited at -30 kV.

Color analysis of the powders accumulated on the + VE and -VE electrodes at an increasing proportion of alumina as additive (Table 1) shows that the additive has the ability to change the relative charge

Blue and red colored polyester particles such that at an alumina content of 0.1% or more by weight, the blue colored polyester is charged with a negative charge and is preferably deposited on the + ve electrode. This behavioral change is also reflected in the spraying, in which the blue polyester is now preferably deposited at -30 kV.

The data from Table 1 is also shown in Figure 8, where the difference in coloration, deltaE between the plates is plotted against the alumina concentration. For better representation, the difference to red is shown as a positive value and the deviation to blue is a negative value from the zero point, which means that there is no difference in color between the plates. It is apparent from the graph that the critical concentration of alumina additive is between 0.05 and 0.1%, vice versa, the polarity of the friction charge is partial or complete, with the result that the same number of red and blue polyester particles have a positive and negative charge and the electrostatic charge separation of the particles is therefore minimal as can be shown by a deltaE value of zero or at most +0.5. However, it is also apparent that this concentration of alumina is too small (less than 0.1%) and thus insufficient to ensure sufficient powder flow, and almost no change in the alumina content.

Experiment II parts of the red-colored polyester powder was mixed with 50 parts of the blue-colored polyester powder and the additives were added individually in different concentrations. Each sample is mixed for 10 seconds in a mixer (Moulinex). As in Test I, the samples are then electrostatically sprayed at -30 kV and -70 kV individually on aluminum plates and also at 0 kV voltage on the plates under voltage ± 20 kV. The color analysis of the resulting coating is summarized in Table 2 below

-25GB 287721 B6

Table 2

% wt. -30kV boards compared to -70kV boards + VE compared to -VE delta (D65) deltaA delta (D65) delta A ZnO ^x 1 1,256 redder 0.85 4.42 redder 3.14 ZnO 3 0,68 redder 0.29 1.92 redder 1.66 ZnO 10 0.96 bluer 0.09 1.42 bluer -0.16 ^x Aldrich, particle diameter less than 1 micrometer. CaO ^x 1 1.62 redder 1,22 2.51 redder 1.39 CaO 3 1.73 redder 1,23 3.49 bluer -2.52 CaO 10 0,38 redder 0.30 1.85 bluer -1.31 ^x BDH, all particles smaller than 10 microns. SiO ₂ ^x 1.5 0.16 bluer -0.11 6.71 redder 4.44 SiO ₂ 3 0.41 bluer -0.16 4.92 redder 2.94 ^x Degussa, particle size 2 micrometers. Al (OH) _δ 0.8 4.74 redder 3.43 19.06 redder 12.11 Al (OH) ₃ 3 2.46 redder 1.79 4.02 redder 3.10 A1 (OH) ₃ 10 1.68 redder 1,21 1.10 redder 0.34 MgCO ₃ 1 2.77 redder 1.92 2.64 redder 0.86 MgCO ₃ 3 0.86 redder 0.46 6.20 bluer —4.34 MgCO ₃ 10 2.08 bluer -1.31 5.06 bluer -2.16 Mg ₃ (PO ₄ ) ₂ 1 4.25 redder 3.12 Mg ₃ (PO ₄ ) ₂ 3 0.99 bluer 0.42 Mg ₃ (PO ₄ ) ₂ 10 0.56 bluer -0.09 silicate aluminum 1 5.04 redder 3.70 19.60 redder 13.46 aluminum 3 5.71 redder 3.96 12.62 redder 8.16 aluminum 10 2.76 redder 1.89 4,21 redder 2.39

The results show that each additive has a clear effect in terms of reducing the separation of the individual components at increasing concentrations.

Experiment III parts of red powdered polyester was mixed with 50 parts of blue powdered polyester. 0.8% by weight of aluminum hydroxide and, in addition, alumina were added to the mixture to produce a series of samples having concentrations of 0.2%, 0.3%, 0.4%, and 0.6% alumina. Each of the samples was deposited by electrostatic spraying at -30 kV and -70 kV as well as by spraying 15 at 0 kV on the positive and negative electrodes (± 20 kV). The color analysis of the resulting coatings is shown in Table 3.

-26GB 287721 B6

Table 3

% Al (OH) ₃ 0.8 wt. + A1 ₂ O ₃ % -30kV boards compared to -70kV boards + VE compared to -VE delta (D65) delta A delta (D65) delta A 0 4.74 redder 3.43 19.06 redder 12.11 0.2 0.43 redder 0.27 1.63 redder 1.45 0.3 0.53 bluer -0.20 3.40 bluer -1.87 0.4 0.71 bluer -0.28 4.47 bluer -2.80 0.6 0.43 bluer -0.20 2.69 bluer -1.57

The data from Table 3 is shown graphically in Figure 9, which shows the color difference between the 5 plates depending on the alumina concentration. For better representation, the difference to red is shown as a positive value and the difference to blue is a negative value relative to the zero point, which means zero difference in color between the two plates.

It can be seen from FIG. 9 that when the process is compared to the use of alumina alone in test I, 0.8% by weight of aluminum hydroxide is added

(a) the need to increase the proportion of alumina under appropriate conditions, ie between 0,2 and 0,3% by weight; and

(b) to reduce the segregation of the components throughout the alumina concentration range.

These effects are clearly illustrated in Figure 10, comparing the results of Experiments I and III for samples that were electrostatically deposited at -30 kV and -70kV.

Thus, in order to achieve a beneficial effect when using the combination of ingredients of the invention, one or both of the components must reduce the tendency of the powder mixture to split into individual color particles, as mentioned above, while the other component should reduce the concentration additives and conditions.

An experiment of IV parts of red powdered polyester was added to 50 parts of blue powdered polyester and in addition various additives or combinations of ingredients were added as shown in Table 4 below. The material for each sample was mixed in a mixer (Moulinex) and then applied in the form of spraying as described above in Experiments I to III. Table 4 summarizes the color analysis data of the resulting coatings.

-27GB 287721 B6

Table 4

Additive or combination,% -30kV boards compared to -70 kV boards + VE compared to -VE delta (D65) deltaA delta (D65) deltaA ZrO ^x ₂ 1.5 2.99 redder 1.58 12.04 redder 7.74 1,5γΟτ 1.5 + AI7O3 0.2 0.76 bluer -0.02 2.05 bluer -0.97 ZrO ₂ 1.5 + Al-> O ₃ 0.4 0.3 bluer -0.26 2.92 bluer -0.78 ^x Aldrich, particle size less than 5 microns. SiO ₂ 1.5 0.16 bluer -0.11 6.71 redder 4.44 SiO ₂ 1.5 + Al ₂ O ₃ 0.2 0.27 redder 0.0 1.42 redder 0.95 SiO-> 1.5 + Al-> O ₃ 0.4 0.34 bluer -0.15 2.7 bluer -1.44 ZnO 1 1.24 redder 0.85 4.42 redder 3.14 ZnO 1 + Al ₂ O ₃ 0.2 0.59 bluer -0.15 3.74 bluer -1.59 ZnO 1 + Al ₂ O ₃ 0.4 0.54 bluer -0.31 5.66 bluer -3.12 CaO 3 1.73 redder 1,23 3.49 bluer -2.52 CaO 3 + Al ₂ O ₃ 0.2 1.37 bluer -0.56 3.88 bluer -2.24 CaO 3 + Al ₂ O ₃ 0.4 0.66 bluer -0.28 2.56 bluer -1.60 silicate aluminum 1 5.04 redder 3.70 19.60 redder 13.46 + A1 ₂ O ₃ 0.2 1.4 Redder 1.05 2.32 redder 2.05 + A1 ₂ O ₃ 0.4 0.87 bluer -0.23 2.53 bluer -1.08

Obviously, each of the combinations of ingredients that were tested generally had the properties discussed in the discussion for Experiment III above.

Experiment In parts of red epoxy polyester, 50 parts of white epoxy polyester were mixed and blended in a blender (Moulinex) for 10 seconds. Then the mixture was electrostatically sprayed at -30 kV and -70 kV on aluminum plates. The plates were then heated to 200 ° C for 15 minutes. Electrostatic spraying was very difficult as the material blocked the gun and accumulated in it. The color difference of both plates was delta E (D65) = 455 and delta C (D65) = 3.66 (redder).

The same powder mixture was also sprayed onto individual aluminum plate electrodes at +20 kV and -20 kV, the color difference between the two plate electrodes was deltaE (D65) - 8.19, the deltaC (D65) color difference = 12.89 (redder) .

To evaluate the effect of the alumina additive, a powder mixture was prepared in the same manner as above and the individual samples of this mixture were mixed with two different concentrations of alumina C. Then each sample was applied by electrostatic spraying at a voltage of -30 kV and -70 kV . The samples were also sprayed without voltage to individual aluminum plate electrodes at +20 kV + -20 kV. The color analysis of the resulting coatings is shown in Table 5 below.

-28GB 287721 B6

Table 5

AI2O3 content -30kV boards compared to -70 kV boards + VE compared to -VE delta (D65) deltaC delta (D65) deltaC O 4.55 redder 3.66 18,19 redder 12.89 0.05 4.33 whiter -2.52 6.86 whiter -2.65 0.1 5.63 whiter -3.52 9.16 whiter -4.10

The plate electrodes reflect the positive and negative nature of the powder mixture components. In the absence of alumina as an additive, a white epoxypolyester is deposited on the negative electrode, meaning that its particles have been positively charged when rubbed with the red epoxypolyester particles. Conversely, the red epoxy polyester is deposited on the + ve electrode, which means that it has been charged with a negative charge. This behavior of the particles is also reflected in spraying experiments at different voltages, in which, in the absence of additives, negatively charged red particles are preferentially deposited at -30 kV.

The color analysis of the powders accumulated on the + VE and -VE electrodes at an increasing proportion of alumina as an additive (Table 5) shows that this additive has the ability to vary the relative charge of the white and red epoxy polyesters resulting from friction, so An amount of 0.05% by weight or more leads to a negative charge of the white polyester particles, which is then preferably deposited on the + ve electrode. This change in the behavior of the particles is also reflected in the spray application, in which the white epoxypolyester is now preferably deposited at a voltage of -30 kV.

Experiment VI parts of the red powdered epoxypolyester was mixed with 50 parts of the white powdered epoxypolyester and the various ingredients were added individually at different concentrations. Each sample is mixed for 10 minutes in a mixer (moulinex). As in Test V, samples were then electrostatically sprayed individually at -30 kV and -70 kV voltages on aluminum plates, and also at 0 kV voltages on plates at ± 20 kV. All plates were then heated to 200 ° C for 15 minutes. The color analysis of the resulting cured coatings is summarized in Table 6 below.

-29GB 287721 B6

Table 6

ingredient% -30kV boards compared to -70kV boards + VE compared to -VE deltaE deltaC (D65) deltaE deltaC (D65) O 4.55 3.66 redder 18.19 12.89 redder A1 (OH) ₃ 5 1.99 0.09 redder 4.66 4.49 redder SiO ₂ 1 4.61 3,04 redder 15.77 11.04 redder 2 1.01 -0.34 whiter - MgCO ₃ 2 1.35 -0.19 whiter 3.89 -1.89 whiter 5 2.27 -1.98 whiter - CeO ₂ 5 1.51 1.48 redder - 8 1.35 -0.38 whiter 5.32 -3.96 whiter ZrO ₂ 3 1.98 1.83 redder 13.69 9.19 redder 10 1.67 1.50 redder 5.32 2.93 redder WO ₃ 5 7.54 5.60 redder 14.69 7.13 redder 10 1.58 0.81 redder 11.90 5,58 redder CaO5 2.96 1.98 redder 4.75 2.55 redder 10 2.77 2.29 redder 2.55 -1.04 whiter silicate 5 1.39 1.05 redder 10.69 7.09 reddish aluminum 8 1.55 -0.20 whiter 8.00 6.35 redder ZnO 1.58 1.30 redder 5.11 -2.58 whiter 5 3.67 -2.25 whiter 7.45 -4.38 whiter Mg ₃ (PO ₄ ) ₂ 3 2.95 2.25 redder 4.95 2,15 redder 8 0.94 -0.59 whiter 5.88 -5.08 whiter borate zinc 5 2.86 1.37 redder 4.18 1.74 redder 10 4.44 2.93 redder - BaTiO ₃ 3 4.47 2.99 redder 7.56 13.88 redder 8 1.86 1,78 redder 7.41 8.16 redder MoO ₃ 5 2.61 2.38 redder 15.02 9.53 redder

The results show that each additive has a distinct effect against material separation at increasing concentration.

Experiment VII

In order to further demonstrate the effect of alumina on the electrostatic spraying behavior of powdered materials using powder blends, 50 parts of red polyester and 50 parts of blue polyester were mixed and blended for 10 seconds in a blender (Moulinex). Then the mixture was applied by electrostatic spraying at -30kV and -70 kV voltages on aluminum plates. The plates were heated to 200 ° C for 15 minutes. The difference between the plates was deltaE (D65) = 2.69 and deltaA (D65) = 0.71 (redder).

The same powder mixture was also sprayed on individual aluminum plate electrodes at +20 kV and -20 kV, the color difference between the two plate electrodes was deltaE (D65) = 8.30 and deltaA (D65) = 6.3 (redder).

To demonstrate the effect of the alumina additive, a mixture of the same colored powder materials as above was prepared and different amounts of alumina C were added to each sample. Each sample was then sprayed at -30 kV and -70kV voltages. The samples were then heated to 200 ° C for 15 minutes. In addition, the samples were applied

-30GB 287721 B6 Voltage-free spraying on aluminum plate electrodes at ± 20 kV. The electrodes were heated to 200 ° C for 15 minutes, the color analysis of the resulting coatings is shown in Table 7 below.

Table 7

Content A1 ₂ O ₃ % -30 kV plates compared to -70 kV plates electrodes + VE compared to -VE electrodes deltaE deltaA deltaE deltaA 0.0 2.69 0,71 redder 8.30 6.3 redder 0.1 0.49 -0.34 bluer 6.11 -5.11 bluer 0.2 1.06 -0.86 bluer 2.54 -0.22 bluer 0.6 2.63 -2.12 bluer 8.65 -7.01 bluer 1.0 2.35 -2.31 bluer 5.44 -2.55 bluer

The plate electrodes reflect the positive and negative nature of the powder mixture components. In the absence of alumina as an additive, the blue polyester is deposited on the negative electrode, which means that it has been positively charged by friction with the particles of red polyester. On the other hand, red polyester is deposited on the positive electrode, which means that it has a negative charge due to friction. This is also reflected in the spray application, in which, in the absence of the additive, the negatively charged red powder material is preferably deposited at -30 kV.

The analysis of the coloring of the powders on the + VE and -VE electrodes with increasing amounts of alumina as additive is summarized in Table 7 and shows that the additive has the ability to change the relative charge of blue and red polyester so that at 0.1% by weight or more alumina the blue polyester charges negatively and is preferably deposited on a positively charged electrode. This change is also reflected in the spray, in which the blue polyester is now preferably deposited at -30kV. It is likely that at a certain critical concentration of alumina as an additive between 0.0% and 0.1%, the polarity changes and at the same time the same number of red and blue polyester particles has a positive and a negative charge and virtually no separation of the mixture based on this charge. However, this concentration of alumina is too small to ensure sufficient flowability of the powdered material and, moreover, the concentration can be changed only slightly and the desired effect is no longer present, which means that this equilibrium state is very sensitive to slight variations in alumina content.

Experiment VIII parts of red polyester powder was mixed with 50 parts of blue polyester powder. Various concentrations of the additive mixture, which is composed of alumina mixed with aluminum hydroxide, are then added to the formed mixture after dry mixing of these components.

The additive mixture was made by mixing alumina and alumina in relative concentrations of 10: 90% by weight in a mixer (Moulinex) for a total of 1 minute. Then, the obtained additive mixture was added in concentrations of 1, 2 and 3% by weight to the mixture of red and blue polyester powder up to concentrations of alumina of 0.1, 0.2 and 0.3% by weight. Each sample was mixed in a mixer (Moulinex) for 10 seconds and then sprayed at -30 kV and -70 kV. The samples were then heated to 200 ° C for 15 minutes and analyzed, the color analysis results are shown in Table 8.

-31 GB 287721 B6

Table 8

AKOHVALC concentration) 90: 10 (%) -30 kV panels compared to -70 kV panels deltaE deltaA 0 2.69 0,71 redder 1 (0.1% Al ₂ O ₃ ) 1.16 1.09 redder 2 (0.2% Al2O3) 0.25 0.00 Redder 3 (0.3% Al2O3) 0.47 0,32 redder

The following effects have been shown to occur when using a mixture of alumina and alumina compared to alumina alone:

(a) the proportion of alumina to be added to achieve the corresponding conditions is increased up to> 0,3% by weight; and

(b) particle separation within the alumina concentration range is reduced.

Thus, to obtain the full benefit of the use of the additive combinations of the invention, one or both of the components need to reduce the tendency of the powder mixture to split into the individual components as described above, while the other component has to reduce dependence on additive concentration changes.

Experiment IX parts of red powdered polyester was mixed with 50 parts blue powdered polyester and in addition various additives or additive mixtures were added as shown in Table 9 below. All ingredients were made by mixing the relative proportions of the two components listed in the table for 1 minute. in a mixer (Moulinex). The additive was then added to the blue 25 and red powdered polyester in the blend, the resulting blend was blended for 10 seconds in the same blender. The obtained samples were sprayed at -30 kV and -70 kV onto aluminum plates, which were then heated to 200 ° C for 15 minutes. The results of the color analysis are shown in Table 9 below.

-32GB 287721 B6

Table 9

an additive or combination of additives -30 kV panels compared to -70 kV panels deltaE deltaA Al ₂ O 3 / SiO ₂ mixture (20%: 80%) 1% (0.2% Al ₂ O ₃ ) 0.59 -0.16 bluer 2% (0.4% Al2O3) 0.37 0.01 redder AbO 3 / ZnO mixture (20%: 80%) 1% (0.2% Al2O3) 1.31 -0.93 bluer 2% (0.4% Al2O3) 0.70 -0.57 bluer AhOj / MgCO3 mixture (20%: 80%) 1% (0.2% Al2O3) 1.17 0.14 redder 2% (0.4% Al2O3) 0.20 0.01 redder AhCh / aluminum silicate (60%: l 10%) 1% (0.6% A1 ₂ Oj) 0.80 0,61 redder 1.5% (0.9% Al2O3) 0.58 -0.34 bluer AWCeCh mixture (10%: 90%) 2% (0.2% Al2O3) 1.00 -0.84 bluer 3% (0.3% Al2O3) 1,02 -0.29 bluer Al2O3 / WO3 mixture (10%: 90%) 2% (0.2% Al2O3) 0.66 -0.06 bluer 3% (0.3% Al2O3) 0.26 0,13 redder Al ₂ O ₃ / Mg ₃ (PO ₄ ) 2 mixture (10%: 90%) 1% (0.1% Al ₂ O ₃ ) 1.55 0,99 redder 3% (0.3% Al2O3) 1.37 -0.19 blue ΑΙ2Ο3 / Ζ1Ό2 mixture (20%: 80%) 1% (0.2% Al2O3) 0.92 -0.54 bluer 2% (0.4% Al2O3) 0.62 -0.48 bluer AhCh / zinc borate (10%: 90%) 1 = (0.1% Al ₂ O ₃ ) 1.76 0.18 redder AbOj / BaTiOj (20%: 79%) 1% (0.2% Al ₂ O ₃ ) 0.95 -0.51 bluer Al ₂ O ₃ / CaO (10%: 90%) 2% (0.2% Al ₂ O ₃ ) 0.66 -0.27 bluer

PATENT CLAIMS

Claims (22)

PATENT CLAIMS CLAIMS 1. Powder coating materials comprising at least one polymeric film-forming material and at least two dry-blended ingredients selected from said dry, particulate, inorganic, dry-blended material. , water-insoluble materials, namely ceramic or mineral materials and / or oxides, mixed 15 oxides, hydrated oxides, hydroxides, oxide hydroxides or oxygenated metal salts and metalloids, wherein at least 95% by volume of the powder coating material has a particle diameter of at most 50 micrometers. Powder materials according to claim 1, characterized in that at least 20% by volume of the bulk powder material has a particle size of 10 microns or less, preferably having a particle size of 30, 40 or 50% by volume. -33GB 287721 B6 Powder materials according to claim 1 or 2, characterized in that 95 to 100% by weight of the material has a particle size of less than 50 microns. Powder materials according to any one of claims 1 to 3, characterized in that 45 to 100% by volume of the particles of this material have a particle size of less than 20 microns. Powder materials according to any one of claims 1 to 4, characterized in that 20 to 100% by volume of the material has a particle size of less than 10 microns. Powdered materials according to any one of claims 1 to 5, characterized in that 5 to 70% by volume of said powdered material has a particle size of less than 5 microns. Powder materials according to any one of claims 1 to 6, characterized in that the d (v) _{50 value} for the material is in the range of 1.3 to 20 micrometers, wherein d (v) ₅₀ is the particle diameter value below which the average of 50% by volume of the particles in the mixture lies. Powder materials according to claim 1, characterized by a particle size distribution in percent by volume according to any of the following schemes: > 95% or> 99% or 100% <45 micrometers <45 micrometers <45 micrometers, or <40 micrometers <40 micrometers <40 micrometers, or <35 micrometers <35 micrometers <35 micrometers, or <30 micrometers <30 micrometers <30 micrometers, or <25 micrometers <25 micrometers <25 micrometers, or <20 micrometers <20 micrometers <20 micrometers, or <15 micrometers <15 micrometers <15 micrometers, or <10 micrometers <10 micrometers <10 micrometers, or Powdered materials according to one of Claims 1 to 8, characterized in that one or both dry-blended ingredients form an oxide or a mixed oxide. Powdered materials according to one of Claims 1 to 8, characterized in that the dry-mixed additives consist of an oxide or a mixed oxide together with a hydrated oxide, hydroxide or oxide-hydroxide. Powdered materials according to any one of claims 1 to 8, characterized in that the dry-blended ingredients comprise: (A) an additive selected from the group consisting of alumina, aluminum hydroxide, calcium oxide, silica, zinc oxide, zirconium oxide, molybdenum oxide, cerium oxide and tungsten oxide, preferably alumina or silica, and in particular alumina; and B) an additive selected from the group consisting of aluminum hydroxide, aluminum silicate, zirconium oxide, zinc oxide, silica and calcium oxide, preferably aluminum hydroxide. Powder materials according to one of Claims 1 to 11, characterized in that one of the dry-mixed additives is alumina. Powdered materials according to claim 12, characterized in that the dry-blended additives comprise alumina and aluminum hydroxide. -34GB 287721 B6 14. Powder materials according to claim 12, characterized in that the dry-mixed additives comprise alumina and aluminosilicate. Powder materials according to one of Claims 1 to 14, characterized in that the total dry-blended additive content of the powder coating material is between 0.01 and 10% by weight, based on the total the weight of the material without additives, preferably at least 0.05% by weight and in particular at least 1.0% by weight. Powder materials according to one of Claims 1 to 15, characterized in that one of the dry-blended ingredients is alumina, which constitutes at least 0.01% by weight, based on the total weight of the material without additives. %, preferably at least 0.02% by weight and in particular 0.2 to 0.4% by weight. Powder materials according to one of Claims 1 to 16, characterized in that one of the dry-blended ingredients is alumina and the total amount of the other additive (s) does not exceed 5% of the total weight of the formulation without additives, preferably does not exceed 3% . Powder materials according to one of Claims 1 to 17, characterized in that the particle size of each of the dry-blended ingredients does not exceed 5 microns, preferably 2 microns, and in particular does not exceed 1 microns. Powder materials according to any one of claims 1 to 18, characterized in that they comprise only one coating component, namely a film-forming polymer, a hardener and optionally one or more coloring agents. Powder materials according to any one of claims 1 to 18, characterized in that they comprise two or more coating components, each comprising a film-forming polymer, optionally a hardener and optionally one or more colored substances. Powder materials according to claim 20, characterized in that each of the coating components has a different color. Powder materials according to any one of claims 1 to 21, characterized in that the film-forming polymer or each film-forming polymer is selected from the group of carboxyl-functional polyester resins, hydroxyl-functional polyester resins, epoxy resins and acrylic functional resins. resins.